Sunday, June 19, 2022

County Health Rankings and COVID Case Mortality

I finished being at the Juneteenth festivities in Johnstown and am ready to get back to county health rankings (CHR) and local COVID numbers. Case mortality (the number of deceased divided by the number of cases) will be the focus of this post. Two weeks ago, I focused on vaccination rates in the 10 county region. Case mortality and vaccination rates were negatively correlated (meaning that as one variable increases the other decreases) accounting for 54% of the variability. There were eight other CHR statistics correlated with vaccination rates. Eighteen other CHR statistics were correlated with case mortality. 

The correlation with the average number of mentally unhealthy days in the last month is summarized in the graph above. The graph shows a strong positive relationship with case mortality accounting for 70.1% of the variability. The regression equation states that for every one day increase in the average number of mentally unhealthy days there is a predicted 1.5% increase in the case mortality rate. There is also a significant but weaker negative correlation that I summarized two weeks ago between mentally unhealthy days and COVID vaccination rates accounting for 42.2% of the variability.  The % of the variability accounted for is simply the correlation coefficient squared.



The strongest negative correlation for case mortality is with the % in the county who are vaccinated for the flu. This correlation accounts for 79.9% of the variability in COVID case mortality. The regression equation says that for every 1% increase there is a predicted 0.06% decrease in case mortality rate. If 100% of the variability were accounted for, all of the counties would fall on the regression lines. Surprisingly this relationship is even stronger than the one with case mortality and COVID vaccination rates which were also negative and only accounted for 54% of the variability.

The 18 significant correlations are summarized in the table below. The positive correlations were with years of potential life lost, both the average number of physically and mentally unhealthy days, % smokers, % physically inactive, the teen birth rate, % unemployed, the social association rate, the injury death rate, and the % who drive alone to work. The negative correlations are as follows: the % with access to exercise opportunities, the % with an annual mammogram, % with flu vaccinations, % completed high school, % with at least some college, the higher the income level in the 80th percentile in the county, the % with severe housing problems and those with a high housing cost burden.

Variable Correlated with Case Mortality

Correlation Coefficient

% Variability Explained

Years of Potential Life Lost Rate (YPLL)

0.741

54.9%

Average Number of Physically Unhealthy Days

0.690

47.6%

Average Number of Mentally Unhealthy Days

0.837

70.1%

% Smokers

0.840

70.5%

% Physically Inactive

0.771

59.5%

% With Access to Exercise Opportunities

-0.662

43.9%

Teen Birth Rate

0.705

49.8%

% With Annual Mammogram

-0.625

39.0%

% Vaccinated for the flu

-0.894

79.9%

% Completed High School

-0.673

45.2%

% Some College

-0.721

51.9%

% Unemployed

0.734

53.9%

80th Percentile Income

-0.796

63.4%

Social Association Rate

0.662

43.8%

Injury Death Rate

0.664

44.1%

% Severe Housing Problems

-0.634

40.2%

Severe Housing Cost Burden

-0.698

48.7%

% Drive Alone to Work

0.732

53.6%


One should always be careful about inferring cause and effect relationships between  correlated variables. Variable A could cause variable B or vice versa. There is always a potential 3rd variable that could explain the correlation such as poverty. Many of these variables are also correlated with each other. This method does allow one to see how they could be interrelated. Next I will look at how different ethnicities correlate with case mortality.

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